THERMOGRAVIMETRY (TGA) – A thermal curve of each material is obtained by means of a thermal analyzer with a thermogravimetric module. The test method is described in the Standard Test Method for Rapid Thermal Degradation of Solid Electrical Insulating Materials by Thermogravimetric Method, ASTM D 3850, except that the specimen is to be heated at 20°C (36°F) per minute in a nitrogen atmosphere. The upper temperature limit is material dependent, with 650°C as the minimum. The purge gas is not changed to air for the percent ash determination. This analysis is further described in the Thermogravimetry sections of the Reference Standard for Electrical Wires, Cables, and Flexible Cords, UL 1581, or the Standard for Polymeric Materials – Short Term Property Evaluations, UL 746A